1. Technical Field
The present invention relates to a multicolor display optical composition, an optical device, and a display method of the optical device and particularly to a multicolor display optical composition employing periodic structures, an optical device, and a display method of the optical device.
2. Related Art
In recent years, display systems/color modulating systems employing color emitting mechanisms of “structural colors” using periodic structural bodies in sub-micro scale (regular structural bodies) have been proposed. To date, color emission of structural colors using periodic structural bodies such as colloidal crystals of mono-dispersion particles of silica and polymers, micro-domain structures of block copolymers, and lamellar structures of surfactants have been reported.
For example, periodic structures each consist of orderly and densely arranged spherical particles, which are a plurality of the structural units, and an externally stimulating unit for stimulating the periodic structures are employed. Structural color alteration is made by changing the cycles of the periodic structures by changing the particle diameter composing the periodic structures by applying voltage by the externally stimulating unit.
A technique enables easy design of switching of opacity and a desired colored state by employing structures having spherical spaces arranged cyclically and filled with a mixture of a compound causing optical isomerization and a nematic liquid crystal, thereby enabling phase transition between nematic phase and isotropic phase of the liquid crystal by optical isomerization of the compound, and accordingly carrying out ON/OFF switching of the reflectivity by reciprocally radiating ultraviolet rays and visible lights and adjusting the wavelength of the reflection peak dependent on the diameter of the spherical space.
A technique enables obtaining various optical properties by forming three-dimensional periodic structures with different refractive indexes in the thickness direction by forming recessed pores in two-dimensional cycles on a substrate formed by cyclically layering a plurality of media with different refractive indexes and etching properties; filling the pores with a liquid crystal; and making the three-dimensional periodic structure variable.
According to a technique, the non-cyclical property of the refractive index can be changed as desired by changing the size of a substrate by applying an external field such as a magnetic field or an electric field to periodic structures formed by cyclically arranging an optical medium in or on the substrate.
From the viewpoint of improving contrast and the like, display devices are required to show white coloration with high degree of whiteness. However, with respect to the above-mentioned techniques, the optical amount is controlled by changing the cycles of the periodic structures by changing the sizes of the spaces of the periodic structures, of the periodic structures themselves, or of the diameters of the particles composing the periodic structures. Moreover, by changing at least one of specific reflection wavelength and transmission wavelength of visible lights, the displayed colors are changed. Although a plurality of different colors can be exhibited, visible lights in the full range of the wavelength cannot be reflected. In other words, it has been difficult to show white coloration. Therefore, since white color can only be exhibited by combining three primary colors reflected from, for example, three different regions, it has been difficult to achieve high reflectivity, i.e., to show white coloration with high degree of whiteness.
With respect to a method of changing the cycles of periodic structures by filling pores of the periodic structures with a liquid crystal, since the light scattering property by the liquid crystal is low and for the same reasons as described above, it has been difficult to show white coloration with high degree of whiteness.